1. Field of the Invention
The present invention relates generally to an apparatus and method for manufacturing wallboard, and more specifically to an apparatus and method for applying reference markings to wallboard during the manufacturing process.
2. Description of the Related Art
Gypsum board is well known and widely used in the construction industry as a convenient way to construct walls, barriers and other structural formations. The use of inorganic gypsum board, which is also commonly known as “wallboard” or “drywall,” is often desirable over more expensive and time consuming conventional wet plaster methods. A typical sheet of wallboard comprises a gypsum core, a back cover sheet on one surface of the core and a face or front cover sheet on the other core surface. One cover sheet is typically folded around the long side edges of the core and overlaps the side edges of the other cover sheet. Apparatuses and methods for the commercial manufacture of wallboard are well known, and instances of such apparatuses and methods can be found, for example, in Kirk-Othmer, Encyclopedia of Chemical Technology, Second Edition, 1970, Vol. 21, pages 621–24, which is incorporated herein by reference. Other examples can also be found in U.S. Pat. Nos. 5,718,797 and 5,879,446, both of which are commonly assigned to the assignee of the present application, and both of which are incorporated herein by reference in their entireties.
Like similar building components make of other materials, gypsum wallboard is normally manufactured into and commercially sold in relatively large standardized sizes, such as 48 inches by 96 inches, 48 inches by 120 inches, 48 inches by 144 inches, and so forth. This wallboard is typically attached to studs, joists, rafters or other types of building supports by use of nails, screws or other types of fasteners. Although some wallboards may be placed and fastened in their entirety, others must be cut to the required size, and both whole and cut boards are typically marked to indicate fixing points for receiving fasteners such as nails or screws.
During construction, a worker typically translates actual measurements of the intended installation to the location and materials at hand, as there are usually sufficiently material deviations in installation techniques and site variances such that reliance on blueprints or drawings for accurately trimming and marking materials is not practical. In practice, construction workers continually measure and mark both materials and target installation sites for the purpose of achieving proper fit, locations for fixing materials, and utilization of wallboard material. The measuring and marking work required for this purpose can be detailed and time-consuming and must be carried out with reasonable care. Such measuring and marking can result in delays in the work, especially when errors are involved, and can result in the use of more wallboard than should be required for a particular job. Such a waste in construction materials is undesirable. In addition, because labor is typically one of the costliest components in construction, excess time or any time needed for such measuring and marking work is particularly undesirable.
Accordingly, there exists a need for wallboard that is fabricated with existing reference markings in a way that is generally useful for construction workers. Such a need has been addressed to some degree, such as by, for example, U.S. Pat. Nos. 4,858,402; 4,870,788; 4,927,696; 5,950,319 and 6,012,255, all of which are incorporated herein by reference in their entireties. Each of these references discusses various needs and solutions for reference or grid markings on wallboard or like construction materials, and each discusses various methods of implementation and use for their solutions. Only one of these references, however, actually refers to a method or apparatus for applying such markings to a wallboard; and this reference, U.S. Pat. No. 4,858,402, only briefly discusses a “marking roller” that crudely applies markings after a wallboard has already been made.
In fact, while many different types of lines, patterns and markings may be desirable, the actual application of markings to wallboard is not trivial. Commercial manufacture of gypsum wallboard is often accomplished by processes that are capable of operation under continuous high speed conditions. Generally, wallboard is conventionally produced by sandwiching a core of aqueous “slurry” or paste of calcined gypsum and other materials between two extremely long and continuous sheets of board cover paper. Various types of cover paper are known in the art, and all such types can be used for this purpose. This cover paper is typically creased during an automated process to form the sides of the wallboard just before it meets with the slurry. After the gypsum slurry has set (i.e., reacted with the water from the aqueous slurry) for a period of time, the resulting extremely long board is then cut into manageable sections. These sections are then fully dried in heating kilns and the finished product becomes a strong, rigid, fire-resistant building material, which is then cut into various board sizes as desired. Cut boards of like sizes are then bundled into large stacks which are then sold and shipped to various wholesale or retail entities.
The foregoing manufacturing process does not naturally lend itself to the application of a “marking roller” or another like marking material. As an initial matter, the marking of wet wallboard is entirely impractical. Furthermore, pre-marking of the very large rolls of cover paper used in a conventional manufacturing process is problematic for a number of reasons. Firstly, cover paper can tend to expand and contract slightly from the time it is pre-marked up until the time that it actually meets the slurry. Secondly, the creaser elements in most manufacturing processes have some degree of flexibility to them, which results in cover paper not being creased in exactly the same location throughout the manufacturing process. In addition, if any pre-marked lines happen to be slightly offset for whatever reason, there exists no convenient way to correct for this offset in conventional wallboard manufacturing systems.
Accordingly, the markings discussed in the references listed above tend to be made by unbundling shipped stacks of wallboards and then marking them as desired. Alternatively, markings could possibly be applied between the heating kiln and bundling stages for wallboard manufactured by a commercial manufacturing process, although such a process typically does not allow for the space, time and labor that would be required for such an operation. As can be readily understood, both an unbundling and marking technique and a kiln-marking-bundling technique incorporate a substantial amount of additional time and effort than is typically required in the manufacture of wallboard. Furthermore, neither technique provides a method for marking wallboard during the actual manufacturing process, as this process has technically ended after the kiln and cutting stages. While they are thus serviceable due to the desirable resulting product, both of these potential marking techniques are largely inefficient ways for providing reference markings on wallboard.
Accordingly, there exists a need for an apparatus and method for applying reference or grid markings to wallboard during the manufacturing process, and in particular for such an apparatus and method to be capable of being incorporated into a wallboard manafacturing process with minimal adaptation or alteration to such a process.